1. Field of the Invention
This invention relates to a process for etching silicon dioxide. More particularly, this invention relates to a process for selectively plasma etching silicon dioxide on a silicon semiconductor wafer which will anisotropically etch openings in the silicon dioxide having near vertical sidewalls while maintaining a high selectivity for silicon.
2. Description of the Related Art
In the etching of openings in a silicon dioxide layer, for example, over a silicon substrate or a polysilicon layer, it is known to use a mixture of argon, CHF.sub.3, and O.sub.2, in a plasma etch process to enhance resist faceting to achieve an in situ tapered contact etch.
Quite surprisingly, however, it has now been discovered that silicon dioxide can be etched to provide near vertical sidewalls, rather than a tapered opening, using an etch chemistry highly selective to silicon, i.e., one which will preferentially etch silicon dioxide rather than silicon, and wherein the amount of selectivity can be controlled by varying the chemistry while still providing a near vertical etch.